I think this has something to do with the Elytra, since it didn't happen before the Combat Update. My avatar will, at random times, start moving around as if gliding in the air in an Elytra, even if I am on the ground without an Elytra equipped. During these short bouts that last about ~10-20 seconds (just a rough estimate, I never timed it) I lose most or all control over the player. It seems to only happen outside. It's especially annoying when it happens at night, because you might glide right into the arms of a zombie or spider and get killed or sustain damage to you and your armor that would not have happened normally. The bug seems to happen randomly, I do not know how to reproduce it. The bug can occur in both creative and survival mode. I was playing 1.10 when it last happened, so it has not been fixed in the new update.